Roentgen-ray apparatus.



. Patented Sept. 4, |900. w. s. ANDREWS. 'nul-:maan BAY APPARATUS.-

(Application Bled Jan. 20, 1898.) (N0 Model.)

UNITED STATES PATENT OFFICE.

WILLIAM S. ANDREWS, OF SCHENECTADY, NEW YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW YORK.

ROENTG EN-RAY APPARATUS.

sPEcIFIoATIoN forming part of Letters Patent No. 657,378, dated september 4, 19oo. Application filed January 20, 1898. Serial No. 667,198. (No model.)

To a/ZZ whom it may concern:

Beit known that I, WILLIAM S. ANDREWS, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Roentgen-Ray Apl paratus, (Case No. 706,) of which the following is a specification.

My invention relates to Roentgen-ray apparatus, and comprises a method and means by virtue of which the vacuum of the tube may be adjusted and maintained continuously at any desired point.

In the practice of my invention I use any form of Crookes tube that contains some chemical-as, for example, caustic potash` preferably placed in a chamber or recess in the tube, which is capable of liberating a gas or vapor when heated. It is well known that when by reason of long-continued use or for any other reason the vacuum becomes too high for the particular purpose to be served the application of heat to this chemical in any way-as, for example, by the passage therethrough of an electric discharge, as shown in patent to Howell, No. 594,156- will liberate a gas or vapor that will reduce the vacuum by au amount depending upon the amount of heat applied. It is the aim of my present invention to make such tubes automatic in their action, and I accomplish this result by taking a connection from some point whose electromotive force is dependent upon the condition of the vacuum in the tube to a condenser or other device which has capacity to absorb and return or dissipate electric energy. The amountV of electric energy absorbed and returned or dissipated by such a device will vary with its size, form, and nature and also with the condition of the vacuum in the tube. By passing the current flowing to the said body through a heater surrounding the chemical or through the Howell device or any of its equivalents I am enabled to automatically maintain a certain particular degree of vacuum, and by adjusting the capacity of the body to absorb energy or by adjusting the frequency or voltage of the current supplied to the tube I am able to adjust the vacuum for the production of X -rays having any desired penetrative eects.` However, it is not necessary that the electric enhergy be returned to the circuit, and any suitable device may be connected with the abovedescribed source of current which will cause the current when the vacuum in the tube is raised to pass through the path in proximity to the gas-yielding body, whether this energy be dispersed in space or to ground or returned to its source by the same path. All such devices under the name of capacity devices or condensers are included Within the scope of my invention.

In the drawings attached to this specification, Figure l is a general view of my improved apparatus in its preferred form. Fig. 2 is a detail View. Fig. 3 is a view of a modification, and Fig. 4 is a view of my improved heating device.

In Fig. l, A is a source of alternating current feeding a tension-raising transformer T. The secondary of this transformer charges a condenser K, which discharges with au oscillatory discharge through the spark gap 1 formed between the points P P and the primary of the transformer T in series. This is the now well-known high-frequency apparatus. The secondary of the transformer T' supplies current to the two terminals B B', to which are connected the two terminals C C of a tube D. (Here shown as of the doublefocus type.) Connected to the tube D and part thereof is the recess or chamber E, with terminal C2, in which is placed the chemical F. Connected to the terminal C2 by a wire Z is shown a condenser-plate or capacity device Gr, which may, for example, consist of a sheet of tin-plate suspended in the air by a thread of cotton or other insulating material. The operation of this device I understand to be as follows: An alternating electromotive force isinduced in the secondary of the transformer T', which electromotive force causes currentto flow in the connections and through the tube in the usual way. Obviously the absolute potential above the earth of any point in this circuit will be alternating in character. C. .This point will be the seat of an altermating potential, and speaking from the static point of view rather than from the electromagnetic point of view it will` be alternately positive and negative. The magnitude of the positive and negative maxima of this po- Consider, for instance, the point IOO tential Will dependVv upon the state of theV higher the vacuum in the tube thegreater will be theiv'ariation ofT absolute potential and the maxima of absolute potential at the point C2, and the greater Will be the magnitude of this current. Suppose that at the start the vacuum of the tube is too high. The charging and discharging current will` iiow through the chemical F and liberate vapor, which will lower the vacuum. When the vacuum has been sufficiently reduced, currenty will pass through thetu be from I-I' to H,. and the static potential at the plate Hwill not-vary sufficiently to cause any considerable charge and discharge through the bran ch E to the condenser-plate G, so the liberation of vapor Will cease. When the vacuum again rises by the gradual condensation of the liberatedvapor in the tube, a1 chargingand discharging current will again pass through the portion E, and the operation will be repeatedz For adjusting the vacuum I may obviously adjust either the capacity of the condenserplate G or the frequency or voltage of the current supplied. Fork example, I may con= nect the terminal C2 with the wire Z and attach to this wire one large plate G and one l or more smaller plates G. In this way the amount Vof .current flowing. through the lportion E of the tube, and therefore the amount of vapor liberated by the chemical F., may be varied at will by adding or removing the plates G; butI findv it more cpnvenientfin practice to regulate the vacuum Afor different degrees of penetration by adjusting the length' of the spark-gap between thepoints P Pi. 'IT accomplish this by mounting, the points vP P,` which are preferably of platinum, in screws Q Q, in a manner shown in Vdetail vin Fig. r29' and providing the screws-Q Qwith insulating handles R R. The screws it in brass posts SS, preferably insulated by the sleevesI L I find that any variation in the length lof the' spark-gap between the points P P will varyy the frequency or electromotive force, or both, of the current in the transformer T. The result of this isto vary the point at which sufficient current, passes into the cond'anserplate G to liberateV gas from the chemical F,

and therefore to vary theV point at which the vacuumfinth'e tube tained... v ,a A

Another great advantage of` thev construction shown in Fig.1 is that it doesv not produce a loud noise, which is usual in the oper# atio'n of apparatuslof this character. In order to providethe draft usually deemed 1U, is also evident that within certain limits the.,

is, automatically main?A necessary with such apparatu sy I mount the posts SS uponlan insulating base-board U, raised by the feet V V and provided with an opening Wand a box or cover X, supporting a removable chimney Y. By this arrangement Iobtain ai simple',- cheap, convenient,` and inearly --noisel'ess source; of` high-frequency currents. ,A i Instead of using` the Howell tube, as shown -fir'r Figa` 11, I1' may: use the form of tube shown .and described in my prior application, Serial .No.v 639,510, filed June 5, 1897, in which the 5 chem ical: chamber" isV surrounded by an elec- ;t'ricfheater ofpeculiar construction. (Shown in detail in Fig. 4. This form of tube is shown in Fig. 3, in which it will be seen that the ter'- Lminal-G- is connected'tov earth through the heater K and the variable-spark-gap N.. The heater may consist of atube of glass or other j-insulating material, in which areplaced al i ternately small pieces of conductingA and insulating material, as more fully described in my above-mentioned application, Aand surrounding the copper tube or SheathL, which serve's to distribute the heat. The copper sheathsurrounds the portion E of the Crookes tu-be D,.and the terminal C2 is absent. One terminal M of the heater is connected to the terminal C of the tube, While t-he terminal yM' may be connected toa condenser-plate, as iis the terminal C2 in Fig. 1. The surging currents passing to and Vfro from the condenserplate through the heater will then act to generate sulicient heat to liberatethe necesi sary amount of gas from the chemical placed iin the end of the tube E'. y

Obviously I may use the earth .in place of `the condenser-plate G with either form of tube, and I may, if preferred, regulatethe lvacuum in the' tube by an adjustable sparkgap or any other adjustable resistance suitable for currents ofv lthe character used in suchapparatus. Such an arrangement' I have ,illustrated in Fig. 3, in which the terminal Nv of the heater, which evidently corresponds to the terminal C2 in Fig. 1, is connected through the adjustable spark-gap N to earth latl O.

Y When the source of current is anordinary induction-coil or other comparatively-feeble source, I find it: preferable to connect the Howell terminal C2, Fig. 1, or` the terminal Mof Fig. 3 direct to earth without the use of a spark-gap, unless the induction-coil is Ione of considerable power, and to regulate lthe vacuum by adjusting the rheotome. v

, `What I claim as new, and desire to secure byI Letters Patent of the United States, is- The method of. maintaining a vacuumtu-be in operative'condition at a predetermined vacuumfwhich consists in passingcurrent through the tube,.andV taking apdischarge lfrom a point in the circuit to a'body capable 2 of absorbing and returningelectrical energy, causing said discharge to vary the vacuum in i the tube,1 and varying the discharge' in accordfancerwith the vacuum in tube.

IOO

IIO

essere s 2'. The combination with a vacuum-tube of a chamber therein, a chemical adapted to liberate vapor or gas upon the application of heat in said chamber, and a connection whereby a discharge passes from the tube to a body capable of absorbing and returning electrical energy, so as to liberate vapor or gas from said chemical.

3. The combination with a vacuum-tube of a chamber therein, a chemical adapted to liberate vapor or gas upon the application of heat in said chamber, a connection whereby a discharge passes from the tube to a body capable of absorbing and returning electrical energy, so as to liberate vapor or gas from said chemical, and means for regulating the amount of said discharge. i

4. The method of varying the discharge of a part of the current in the circuit of an X-ray apparatus, through a gas-yielding body contained within the tube, which consists in adjusting the frequency of the supply-current.

5. The method of varying the capacity of discharge of a part of the current in the circuit of an X-ray apparatus, through a gasyielding body contained within the tube, which consists in varying the length of the spark-gap in the supply-circuit.

6. The combination with a Vacuum-tube of a chamber therein, an element adapted to liberate Vapor or gas upon the application of heat in said chamber, a body having electric capacity and a connection whereby a surging discharge passes from the tube to said body in proximity to said gas-yielding element.

7. The combination of a vacuum-tube having a chamber therein, a chemical adapted to liberate Vapor or gas in said chamber, a terminal in said chamber and a connection from the said terminal to earth.

8. The combination of a vacuum-tube having a chamber therein, a chemical adapted to liberate vapor or gas in said chamber, a terminal in said chamber, and a connection from the said terminal to earth through an adjustable spark-gap.

9. The combination with a source of alternating current, a condenser, an adjustable spark-gap through which the condenser is adapted to discharge a high-frequency electromotive force, and a translating device in series with said spark-gap, the spark-gap terminals being formed of points of refractory material.

10. The combination with a source of alternating current, a condenser, an adjustable spark gap through which a condenser is adapted to discharge a high-frequency electromotive force, and a translating device in series with said spark-gap, the spark-gap terminals being formed of points of refractory material, in combination with a chimney for causing a natural draft across the spark-gap.

11. The `method of maintaining a desired degree of density in an X-ray tube, which consists in causing an increase in the tube resistance due to the decrease in the density thereof, to divert current which liber-ates gas within the tube, and is then absorbed outside the tube.

12. Means for maintaining a desired degree of densityr in an X-ray tube, which comprises a lead from a part of the tube, the electromotive force of which is dependent upon the degree of tube density, a condenser of the capacity required to maintain the tube density at a desired degree, to which condenser said lead is connected, and algas-yielding agent within the tube in the path of the current flowing throughV said lead.

13. The method of determining the vacuum at which the tube of an X-ray apparatus shall operate, that is, of varying the operating degree of tube density which consists in varyin g the capacity of discharge along a path adapted to join the main circuit at one point only and to traverse a gas-yielding body contained within the tube.

14. The combination with a Crookes tube, of a condenser electrically connected therewith, to which current Hows when the resistance of the tube increases owing to the decrease of tube density, and a gas-yielding body within said tube from which gas is liberated by current liowing to the condenser.

15. The combination with a Crookes tube, of a variable condenser electrically connected therewith, and a gas-yielding body Within said tube in the path to the condenser.

16. The combination with a Crookes tube, of a gas-yielding body therein, and means for diverting a part of the line-current through said body along a path adapted to be connected to the tube at only one point, and then dispersing said part.

17. The combination with a Orookes tube,

vof a gas-yielding body therein, a condenser adapted to receive adischarge of part of the line current through said body when the vacuum in the tube rises, and means for regulating said discharge.

1S. The combination with a Crookes tube, of a gas-yielding body therein, a condenser adapted to receive a discharge of part of the line-current when the vacuum in the tube rises, and an adjustable spark-gap in the supply-circuit, whereby said discharge is regulated.

19. The combination with a Crookes tube,

-of a gas-yielding body therein, and means for IOO 

